1. Field of the Invention:
The present invention relates to an improved housing structure for use in lawn mowers of a type which includes a cut-grass discharge passage extending from a cutter blade housing for discharging the cut grass from the cutter blade housing and a separate or discrete bottom plate closing the bottom of the cut-grass discharge passage.
2. Description of the Related Art:
Housing structures for lawn mowers are known, for example, from Japanese Utility Model Laid-open Publication No. SHO-63-61223 and Japanese Patent Laid-open Publication No. HEI-1-218509 which both disclose so-called walking-type lawn mowers. More specifically, Japanese Utility Model Laid-open Publication No. SHO-63-61223 shows that a bottom plate of a cut-grass discharge passage is secured to a cutter blade housing by means of screws, and Japanese Patent Laid-open Publication No. HEI-1-218509 shows that the cut-grass discharge passage has a relatively great level difference on the upper or inner surface of the bottom plate at a portion near an exit (i.e., cut-grass discharge opening) of the passage.
However, with the walking-type lawn mower disclosed in the above-mentioned Japanese utility model laid-open publication, relatively troublesome and difficult operations are required for screwing the bottom plate to the cutter blade housing. If any one of the screws to be used for screwing the bottom plate is lost, the bottom plate can not be properly secured to the cutter blade housing, and thus management of parts has to be performed in an appropriate manner. Further, with the walking-type lawn mower disclosed in the above-mentioned Japanese patent laid-open publication, the level difference on the bottom plate near the cut-grass discharge opening would collide with the cut grass and thereby considerably hinder the cut grass from being discharged smoothly through the discharge passage.
It is accordingly an object of the present invention to provide a housing structure for a lawn mower which can greatly facilitate mounting of a bottom plate of a cut-grass discharge passage and also allows the cut grass to be smoothly discharged through the cut-grass discharge passage without being hindered by the bottom plate.
In order to accomplish the above-mentioned object, the present invention provides an improved housing structure for use in a lawn mower, which comprises: a cut-grass discharge passage for discharging cut grass from a cutter blade housing accommodating a cutter blade, the cut-grass discharge passage having a bottom closed with a discrete bottom plate; a bridge member disposed adjacent and along a width of an entrance of the cut-grass discharge passage and having a concave portion for insertion and retention therein of a front end portion of the bottom plate, the concave portion being defined by upper and lower flanges of the bridge member; and a back plate disposed adjacent and along a width of an exit of the cut-grass discharge passage and having a locking recess or hole, the bottom plate having, on a rear end portion thereof, a projection for fitting engagement with the locking recess or hole of the back plate. In the present invention, the bottom plate is secured to the body of the housing with the front end portion inserted in the concave portion of the bridge member and the projection on the rear end portion fitted in the locking recess or hole of the back plate.
As with the conventional lawn mowers, the cut-grass discharge passage is provided, in the inventive housing structure, for discharging the cut grass cut from the cutter blade housing accommodating the cutter blade, and the bottom of this cut-grass discharge passage is closed with the discrete bottom plate. For mounting the bottom plate, the bridge member is provided adjacent and along the horizontal width of the entrance of the cut-grass discharge passage, and this bridge member has upper and lower flanges together defining a channel-shaped concave portion for insertion and retention therein of the front end portion of the bottom plate. The back plate having the locking hole is provided adjacent and along the horizontal width of the exit of the cut-grass discharge passage. On the rear end portion of the bottom plate, there is formed the projection for fitting engagement with the locking hole of the back plate. In this invention, the bottom plate is secured to the body of the housing with the front end portion inserted in the concave portion of the bridge member and the projection on the rear end portion fitted in the locking hole of the back plate. Such arrangements can greatly facilitate the mounting of the bottom plate and thus can reduce the overall cost of the housing.
In one embodiment of the present invention, the front end portion of the bottom plate has a depressed surface area for reception and retention therein of the upper flange of the bridge member in such a manner that the upper surface of the upper flange received in the depressed surface area lies flush with the upper surface of the bottom plate other than the depressed surface area. When the bottom plate is mounted to the body of the housing, the upper surfaces of the upper flange of the bridge member and the bottom plate lie flush with each other with no level difference therebetween that would collide with and thus prevent the cut grass from being discharged smoothly, so that appropriate and smooth discharge of the cut grass through the discharge passage can be achieved by the present invention.
In one embodiment of the present invention, the housing has an upper rear end recess formed by recessing at least an upper rear end edge of a portion of the housing that extends as an extension of a ceiling portion of the cut-grass discharge passage, and an upper rear end edge region of the ceiling portion adjacent the upper rear end recess is formed as a reinforcing bent portion of a dogleg sectional shape in order to reinforce the thus-recessed upper rear end edge of the housing. The upper rear end recess, thus formed by recessing at least the upper rear end edge of a portion of the housing, allows the cut grass to be discharged smoothly without hitting the above-mentioned upper rear end edge of the housing. Further, the upper rear edge region of the ceiling portion adjacent the upper rear end recess is formed as the reinforcing bent portion that serves to reinforce the thus-recessed upper rear end edge of the housing. Thus, the present invention permits smooth discharge of the cut grass while still maintaining the necessary mechanical strength of the housing.